Generally, ultra-fine particles nanometers in size have been manufactured using flames or a furnace and obtained by collecting them with a filter or causing them to be attached to a collection plate. Since the ultra-fine particles are manufactured at high temperature in the prior art, there are disadvantage in that a great deal of energy is necessary and the collection rate is low. Additionally, ultra-fine particles of metal oxides such as SiO2 or Fe2O3 that fail to be collected cause environmental pollution. There is also a disadvantage in that the ultra-fine particles adhere and cohere to each other at high temperature so that properties thereof are lost.
In the meantime, corona discharge used in the manufacture of the ultra-fine particles, which is a type of discharge in gas, is a phenomenon that occurs when a high voltage is applied between two electrodes, before flames are generated, only a portion with a strong electric field emits light and has conductivity. When both the electrodes are in the form of a plate, a globe with large diameter, or the like, the electric field is nearly uniform. However, if one or two electrodes are a needle type or a cylinder type, the electric field around the electrodes is especially strong, so that partial discharge occurs. The electrons discharged by corona discharge collide against air molecules adjacent thereto, so that numbers of ions with a positive charge are generated. The gas in which electrons and ions with a positive charge are separated from each other is referred to as plasma.
Plasma technology to which the corona discharge pertains is widely used in dry etching, chemical vapor deposition, plasma polymerization, surface modification, sputtering, air purification, and the like, which are disclosed in U.S. Pat. Nos. 5,015,845, 5,247,842, 5,523,566, and 5,873,523.
However, in the conventional plasma technology using electrodes of a needle or cylinder type, there is a problem in that the installation of the electrodes causes the relevant apparatus to be complicated. Particularly, there is a problem in that electrodes of a needle type are easily broken due to deterioration when used for a long time and in that the replacement of the broken electrode causes workability and operationability to deteriorate.